The Root Lock is the most commonly applied lock but also the most complex. It coordinates and combines the energy of the rectum, sex organs, and navel point. Mul is the root, base, or source. The first part of the Mulbandh is to contract the anal sphincter and draw it in and up as if trying to hold back a bowel movement. Then draw up the sex organ so the urethral tract is contracted. Finally, pull in the navel point by drawing back the lower abdomen towards the spine so the rectum and sex organs are drawn up toward the navel point. This action unites the two major energy flows of the body: prana and apana. Prana is the positive, generative energy of the upper body and heart center. Apana is the downward flow of eliminating energy. Mulbandh pulls the apana up and the prana down to the navel point. This combination of energies generates the necessary psychic heat to release the kundalini energy. This lock is applied on the exhale. It can also be applied on the inhale when specified.